Modeling pedogenization of zeolitized tuffs: effects of water and phenolic substances on weathering rates of the Campanian Ignimbrite (yellow facies)

An experimental pedology research project, based on a ‘‘process-system’’ pedogenetic model, was initiated to investigate the weathering of Phlegraean Yellow Tuff (PYT) the yellow facies of the Campanian Ignimbrite with phillipsite > chabazite as representative of the parent rock material as the soil-forming factor. PYT was weathered by water (W) and tannic acid solutions (TA) at concentrations ranging from 36101 to 36104 mmol l1. The most concentrated TA solution (36104 mmol l1) showed the greatest extracting efficiency. Na and K were continually solubilized by W; Al, Ca and Mg contributed to the ionic composition of all the TA supernatants. A significant dissolution of the amorphous component and an associated decrease of the zeolite content, especially phillipsite, were noted. The features of PYT weathered outcomes fitted the ‘‘processsystem’’ model very well. PYT showed a pedogenic potential, in being prone to weathering, as well as in releasing elements of importance for plant settlement and development, such as K, Ca, Mg and Fe